Basic keyboard example for Adafruit Trinket with simultaneous input

TrinketKeyboardEmulator.ino

// 3 button keyboard emulator for the 5V Adafruit Trinket.
// Requires the Trinket Keyboard Library from Adafruit (https://github.com/adafruit/Adafruit-Trinket-USB/archive/master.zip)

#include <TrinketKeyboard.h>

// Array to hold keypresses. Trinket can emulate 3 simultaneously pressed keys
uint8_t pressedKeys[3];

void setup() {
  // Each pin* uses internal pullup resistors 
  // *Place a 470 ohm external pullup resistor between Pin 1 and 5V
  pinMode(0, INPUT_PULLUP);
  pinMode(1, INPUT_PULLUP);
  pinMode(2, INPUT_PULLUP);
  
  TrinketKeyboard.begin();
}

void loop() {
  TrinketKeyboard.poll();

  // All keypresses are stored in the pressedKeys array as KEYCODE_* or 0 (which releases the key)
  if (digitalRead(0) == LOW)
    pressedKeys[0] = KEYCODE_A;
  else
    pressedKeys[0] = 0;

  if (digitalRead(1) == LOW)
    pressedKeys[1] = KEYCODE_S;
  else
    pressedKeys[1] = 0;

  if (digitalRead(2) == LOW)
    pressedKeys[2] = KEYCODE_D;
  else
    pressedKeys[2] = 0;

  // Update the keypress array and emulate
  TrinketKeyboard.pressKey(0, pressedKeys[0], pressedKeys[1], pressedKeys[2]);

  // Brief delay to more closely emulate speed of keyboard input
  delay(50);
}